A known heating element is disclosed in, for example, WO2004/001775A1. Hereinafter, a constitution of the heating element will be described with reference to the drawings. FIG. 18A is a partially cut-away plan view of a conventional heating element, and FIG. 18B is a sectional view for a main portion of the same.
A silver paste is dried to form a pair of electrodes 112 on flexible base substrate 111 that is formed of a mesh and a film. Resistor 113 is formed between electrodes 112. Terminal portion 114 is formed on an end of electrode 112. Cover material 115 is formed to cover them. In terminal portion 114, terminal member (hereinafter as “member”) 116, such as copper foil, is adhered to the end of electrode 112 using conductive adhesive (hereinafter as “adhesive”) 117 to be electrically connected to the electrode. Lead wire 119 is connected to another end of member 116 by solder 118.
Lead wire 119 cannot be directly soldered on electrode 112 that is formed by drying the silver paste. Accordingly, member 116 is adhered to electrode 112 using adhesive 117 to form terminal portion 114, and lead wire 119 is soldered on member 116. Thereby, electrode 112 and lead wire 119 are electrically connected to each other.
In this constitution, member 116 and lead wire 119 relatively firmly adhere to each other by solder 118, but physical and electrical adhesion of electrode 112 and member 116 depends on adhesive 117. In the typical conductive adhesive, conductive particles, such as gold, silver, nickel, and carbon, are dispersed in epoxy resin. However, if resin curable in a room temperature is used in consideration of workability, adhesion strength is not enough.